Billionaire Carlos Slim, from right, Enrique Martinez, Mexico's minister of Agriculture, billionaire Bill Gates, Eruviel Avila Villegas, governor of state of Mexico, and Melinda Gates participate in a ceremonial ribbon cutting at the International Maize and Wheat Improvement Center, known by its Spanish initials as CIMMYT, in Texcoco, Mexico, on Wednesday, Feb. 13, 2013. The group, which performs research for agricultural productivity, opens its research facility this week. Photographer: Susana Gonzalez/Bloomberg via Getty Images

Billionaire Carlos Slim, from right, Enrique Martinez, Mexico's minister of Agriculture, billionaire Bill Gates, Eruviel Avila Villegas, governor of state of Mexico, and Melinda Gates participate in a ceremonial ribbon cutting at the International Maize and Wheat Improvement Center, known by its Spanish initials as CIMMYT, in Texcoco, Mexico, on Wednesday, Feb. 13, 2013. The group, which performs research for agricultural productivity, opens its research facility this week. Photographer: Susana Gonzalez/Bloomberg via Getty Images

Billionaire Carlos Slim speaks during a news conference with Bill Gates, unseen, to announce donations to Mexico's International Maize and Wheat Improvement Center, known by its Spanish initials as CIMMYT, in Texcoco, Mexico, on Wednesday, Feb. 13, 2013. The group, which performs research for agricultural productivity, will open its research facility this week. Photographer: Susana Gonzalez/Bloomberg via Getty Images

Billionaire Carlos Slim speaks during a news conference with Bill Gates, unseen, to announce donations to Mexico's International Maize and Wheat Improvement Center, known by its Spanish initials as CIMMYT, in Texcoco, Mexico, on Wednesday, Feb. 13, 2013. The group, which performs research for agricultural productivity, will open its research facility this week. Photographer: Susana Gonzalez/Bloomberg via Getty Images

Billionaire Carlos Slim, left, speaks while Bill Gates listens during a news conference to announce donations to Mexico's International Maize and Wheat Improvement Center, known by its Spanish initials as CIMMYT, in Texcoco, Mexico, on Wednesday, Feb. 13, 2013. The group, which performs research for agricultural productivity, will open its research facility this week. Photographer: Susana Gonzalez/Bloomberg via Getty Images

Billionaire Carlos Slim, left, speaks while Bill Gates listens during a news conference to announce donations to Mexico's International Maize and Wheat Improvement Center, known by its Spanish initials as CIMMYT, in Texcoco, Mexico, on Wednesday, Feb. 13, 2013. The group, which performs research for agricultural productivity, will open its research facility this week. Photographer: Susana Gonzalez/Bloomberg via Getty Images

Eruviel Avila Villegas, governor of state of Mexico, from left, billionaire Bill Gates, Enrique Martinez, Mexico's minister of Agriculture, and billionaire Carlos Slim wait for the start of a news conference to announce donations to Mexico's International Maize and Wheat Improvement Center, known by its Spanish initials as CIMMYT, in Texcoco, Mexico, on Wednesday, Feb. 13, 2013. The group, which performs research for agricultural productivity, opens its research facility this week. Photographer: Susana Gonzalez/Bloomberg via Getty Images

Eruviel Avila Villegas, governor of state of Mexico, from left, billionaire Bill Gates, Enrique Martinez, Mexico's minister of Agriculture, and billionaire Carlos Slim wait for the start of a news conference to announce donations to Mexico's International Maize and Wheat Improvement Center, known by its Spanish initials as CIMMYT, in Texcoco, Mexico, on Wednesday, Feb. 13, 2013. The group, which performs research for agricultural productivity, opens its research facility this week. Photographer: Susana Gonzalez/Bloomberg via Getty Images

Billionaire Bill Gates listens during a news conference with Carlos Slim, unseen, to announce donations to Mexico's International Maize and Wheat Improvement Center, known by its Spanish initials as CIMMYT, in Texcoco, Mexico, on Wednesday, Feb. 13, 2013. The group, which performs research for agricultural productivity, will open its research facility this week. Photographer: Susana Gonzalez/Bloomberg via Getty Images

Billionaire Bill Gates listens during a news conference with Carlos Slim, unseen, to announce donations to Mexico's International Maize and Wheat Improvement Center, known by its Spanish initials as CIMMYT, in Texcoco, Mexico, on Wednesday, Feb. 13, 2013. The group, which performs research for agricultural productivity, will open its research facility this week. Photographer: Susana Gonzalez/Bloomberg via Getty Images

Billionaire Carlos Slim speaks during a news conference with Bill Gates, unseen, to announce donations to Mexico's International Maize and Wheat Improvement Center, known by its Spanish initials as CIMMYT, in Texcoco, Mexico, on Wednesday, Feb. 13, 2013. The group, which performs research for agricultural productivity, will open its research facility this week. Photographer: Susana Gonzalez/Bloomberg via Getty Images

Billionaire Carlos Slim speaks during a news conference with Bill Gates, unseen, to announce donations to Mexico's International Maize and Wheat Improvement Center, known by its Spanish initials as CIMMYT, in Texcoco, Mexico, on Wednesday, Feb. 13, 2013. The group, which performs research for agricultural productivity, will open its research facility this week. Photographer: Susana Gonzalez/Bloomberg via Getty Images

Billionaire Carlos Slim, from left, Eruviel Avila Villegas, governor of state of Mexico, Thomas Lumpkin, director of the International Maize and Wheat Improvement Center, known by its Spanish initials as CIMMYT, and billionaire Bill Gates, walk to a ribbon-cutting ceremony at the CIMMYT in Texcoco, Mexico, on Wednesday, Feb. 13, 2013. CIMMYT, which performs research for agricultural productivity, opens its research facility this week. Photographer: Susana Gonzalez/Bloomberg via Getty Images

Billionaire Carlos Slim, from left, Eruviel Avila Villegas, governor of state of Mexico, Thomas Lumpkin, director of the International Maize and Wheat Improvement Center, known by its Spanish initials as CIMMYT, and billionaire Bill Gates, walk to a ribbon-cutting ceremony at the CIMMYT in Texcoco, Mexico, on Wednesday, Feb. 13, 2013. CIMMYT, which performs research for agricultural productivity, opens its research facility this week. Photographer: Susana Gonzalez/Bloomberg via Getty Images

Billionaires Bill Gates, left, and Carlos Slim wait for the start of a news conference to announce donations to Mexico's International Maize and Wheat Improvement Center, known by its Spanish initials as CIMMYT, in Texcoco, Mexico, on Wednesday, Feb. 13, 2013. The group, which performs research for agricultural productivity, opens its research facility this week. Photographer: Susana Gonzalez/Bloomberg via Getty Images

Billionaires Bill Gates, left, and Carlos Slim wait for the start of a news conference to announce donations to Mexico's International Maize and Wheat Improvement Center, known by its Spanish initials as CIMMYT, in Texcoco, Mexico, on Wednesday, Feb. 13, 2013. The group, which performs research for agricultural productivity, opens its research facility this week. Photographer: Susana Gonzalez/Bloomberg via Getty Images

Billionaires Bill Gates, left, and Carlos Slim wait for the start of a news conference to announce donations to Mexico's International Maize and Wheat Improvement Center, known by its Spanish initials as CIMMYT, in Texcoco, Mexico, on Wednesday, Feb. 13, 2013. The group, which performs research for agricultural productivity, opens its research facility this week. Photographer: Susana Gonzalez/Bloomberg via Getty Images

Billionaires Bill Gates, left, and Carlos Slim wait for the start of a news conference to announce donations to Mexico's International Maize and Wheat Improvement Center, known by its Spanish initials as CIMMYT, in Texcoco, Mexico, on Wednesday, Feb. 13, 2013. The group, which performs research for agricultural productivity, opens its research facility this week. Photographer: Susana Gonzalez/Bloomberg via Getty Images

Billionaire Carlos Slim, from right, Enrique Martinez, Mexico's minister of Agriculture, billionaire Bill Gates, Eruviel Avila Villegas, governor of state of Mexico, and Melinda Gates participate in a ceremonial ribbon cutting at the International Maize and Wheat Improvement Center, known by its Spanish initials as CIMMYT, in Texcoco, Mexico, on Wednesday, Feb. 13, 2013. The group, which performs research for agricultural productivity, opens its research facility this week. Photographer: Susana Gonzalez/Bloomberg via Getty Images

Billionaire Carlos Slim, from right, Enrique Martinez, Mexico's minister of Agriculture, billionaire Bill Gates, Eruviel Avila Villegas, governor of state of Mexico, and Melinda Gates participate in a ceremonial ribbon cutting at the International Maize and Wheat Improvement Center, known by its Spanish initials as CIMMYT, in Texcoco, Mexico, on Wednesday, Feb. 13, 2013. The group, which performs research for agricultural productivity, opens its research facility this week. Photographer: Susana Gonzalez/Bloomberg via Getty Images

Billionaires Bill Gates, back left, and Carlos Slim wait for the start of a news conference to announce donations to Mexico's International Maize and Wheat Improvement Center, known by its Spanish initials as CIMMYT, in Texcoco, Mexico, on Wednesday, Feb. 13, 2013. The group, which performs research for agricultural productivity, opens its research facility this week. Photographer: Susana Gonzalez/Bloomberg via Getty Images

Billionaires Bill Gates, back left, and Carlos Slim wait for the start of a news conference to announce donations to Mexico's International Maize and Wheat Improvement Center, known by its Spanish initials as CIMMYT, in Texcoco, Mexico, on Wednesday, Feb. 13, 2013. The group, which performs research for agricultural productivity, opens its research facility this week. Photographer: Susana Gonzalez/Bloomberg via Getty Images

Billionaire Bill Gates listens during a news conference with Carlos Slim, unseen, to announce donations to Mexico's International Maize and Wheat Improvement Center, known by its Spanish initials as CIMMYT, in Texcoco, Mexico, on Wednesday, Feb. 13, 2013. The group, which performs research for agricultural productivity, opens its research facility this week. Photographer: Susana Gonzalez/Bloomberg via Getty Images

Billionaire Bill Gates listens during a news conference with Carlos Slim, unseen, to announce donations to Mexico's International Maize and Wheat Improvement Center, known by its Spanish initials as CIMMYT, in Texcoco, Mexico, on Wednesday, Feb. 13, 2013. The group, which performs research for agricultural productivity, opens its research facility this week. Photographer: Susana Gonzalez/Bloomberg via Getty Images

Billionaire Carlos Slim takes notes during a news conference with Bill Gates, unseen, to announce donations to Mexico's International Maize and Wheat Improvement Center, known by its Spanish initials as CIMMYT, in Texcoco, Mexico, on Wednesday, Feb. 13, 2013. The group, which performs research for agricultural productivity, opens its research facility this week. Photographer: Susana Gonzalez/Bloomberg via Getty Images

Billionaire Carlos Slim takes notes during a news conference with Bill Gates, unseen, to announce donations to Mexico's International Maize and Wheat Improvement Center, known by its Spanish initials as CIMMYT, in Texcoco, Mexico, on Wednesday, Feb. 13, 2013. The group, which performs research for agricultural productivity, opens its research facility this week. Photographer: Susana Gonzalez/Bloomberg via Getty Images

Billionaire Carlos Slim listens during a news conference with Bill Gates, unseen, to announce donations to Mexico's International Maize and Wheat Improvement Center, known by its Spanish initials as CIMMYT, in Texcoco, Mexico, on Wednesday, Feb. 13, 2013. The group, which performs research for agricultural productivity, opens its research facility this week. Photographer: Susana Gonzalez/Bloomberg via Getty Images

Billionaire Carlos Slim listens during a news conference with Bill Gates, unseen, to announce donations to Mexico's International Maize and Wheat Improvement Center, known by its Spanish initials as CIMMYT, in Texcoco, Mexico, on Wednesday, Feb. 13, 2013. The group, which performs research for agricultural productivity, opens its research facility this week. Photographer: Susana Gonzalez/Bloomberg via Getty Images

Billionaire Bill Gates speaks during a news conference with Carlos Slim, unseen, to announce donations to Mexico's International Maize and Wheat Improvement Center, known by its Spanish initials as CIMMYT, in Texcoco, Mexico, on Wednesday, Feb. 13, 2013. The group, which performs research for agricultural productivity, opens its research facility this week. Photographer: Susana Gonzalez/Bloomberg via Getty Images

Billionaire Bill Gates speaks during a news conference with Carlos Slim, unseen, to announce donations to Mexico's International Maize and Wheat Improvement Center, known by its Spanish initials as CIMMYT, in Texcoco, Mexico, on Wednesday, Feb. 13, 2013. The group, which performs research for agricultural productivity, opens its research facility this week. Photographer: Susana Gonzalez/Bloomberg via Getty Images